The present invention relates to an artificial knee joint with a clamping member including a peg for attachment onto a thigh shaft, a lower leg part accommodating a leg prosthesis and a joint casing interconnecting the clamping member and the leg part for pivotal movement of the joint. The clamping member swivels relative to the joint casing and presses against a braking member located inside the joint casing when a vertical load is applied to the knee joint. When the clamping member presses against the braking member, pivotal movement of the joint and the lower leg part with the prosthesis is arrested. A traction strap connected between the lower leg part and the casing tends to return the joint or impel the knee joint back into the stretched or straightened position from a bent position.
The fundamental objective in a prosthesis is to bring about the natural coordinated movements of the substituted member of the body as closely as possible. In the case of artificial legs there arises especially the problem that the load braking systems known according to the state of the art are incapable of optimally doing justice to the safety requirements of the elderly. Due to friction contact processes, locomotion processes such as develop during the natural walk sequence are interfered with in a non-physiological manner with the consequence that these load braking systems lead to the wearer of the prosthesis having a fall.
Over and above that, in the knee joint constructions according to the state of the art, the reduction in size of the joints has resulted in dimensions in which braking forces that are capable of holding a knee in a bent position, results in an overstraining of the joint construction and of the material. Not infrequently this causes substantial wear of the friction surfaces, noisy working knee joints and an increased need for servicing.
It is accordingly an object of the present invention to improve the knee joint referred to above so that an uncontrolled flection or pivoting of the joint under a vertical load is contained during bending movement, while all extension or straightening movements of the knee joint remain freely executable. The automatic engagement of a brake lining is made possible hereby. The construction of the knee joint in particular has to be simple and must operate with minimal wear.